CN100395385C - Process for the preparation of lyocell fibers for cords - Google Patents

Abstract

The invention relates to a method for preparing lyocell fibers used in cords in chemical fiber production. Dried pulp with a degree of polymerization of 1000-1450 and 600-850 is mixed in a weight ratio of 100:100/11-50, and the mixed pulp is mixed with concentrated N-methylmorpholine-N-oxide aqueous solution Add it into the dissolving device at a weight ratio of 5:110~10:105, after static swelling and strong stirring at 70~110°C, then raise the temperature to 80~125°C, stir and distill under reduced pressure to N-formazol in the system The water content of the morpholine-N-oxide aqueous solution is 12% to 14%, so as to obtain a brown and transparent spinning solution, which is solidified into fibers by dry-wet spinning; then the fibers are introduced into the multi-stage washing roller , washed with water for 2 to 20 minutes; finally, under the tension of 0 to 1.0 cN/dtex, after continuous drying at 80 to 160 ° C, it is wound into a bobbin. The lyocell fiber obtained by this method has high strength, high modulus, low elongation, and small thermal shrinkage, and is suitable as a new type of high-quality cord.

Description

Process for the preparation of lyocell fibers for cords

technical field

The present invention relates to the preparation method of tire cord in chemical fiber industry, particularly refers to adopting N-methylmorpholine-N-oxide (NMMO) aqueous solution as solvent to spin Lyocell (Lyocell) fiber used as cord technology.

Background technique

Cord is an important skeleton material required to manufacture tires, and bonding it with rubber can improve the strength and dimensional stability of rubber tires. As the skeleton structure material of the tire, the cord must have the following physical properties: 1) High strength and elastic modulus; 2) Good heat resistance, not easy to degrade under wet heat and dry heat; 3) Good fatigue resistance; 4) Dimensional stability 5) Good adhesion with rubber. At present, the materials used for cord mainly include regenerated cellulose fiber (ie viscose fiber), polyester fiber, nylon, aramid fiber, glass fiber and steel wire produced by the traditional viscose process. The use of these materials in cords has been extensively studied and many patents have been formed, among which the patents relating to viscose cords include GB756709, US2626887, US3282039, CN1180334 and the like.

Viscose cord is the earliest cord used in the rubber industry. It has high breaking strength and modulus, good heat resistance, almost no dry heat shrinkage, excellent dimensional stability, easy access to raw materials, and good adhesion to rubber. Good and other advantages, it is an excellent skeleton material for the manufacture of high-performance car radial tires. However, with the development of automobile technology and the need for high-speed driving, the requirements for cords are also getting higher and higher. Since the traditional regenerated cellulose fiber production process, that is, the viscose process, can only use cellulose pulp with a low degree of polymerization (generally DP is 500-800) as raw material, the mechanical properties of the obtained viscose cord, especially the dry and wet modulus Both are not high enough to meet the requirements of high-performance tires. In addition, the production process of viscose fiber uses a large amount of corrosive substances such as alkali and acid, and will release toxic gases such as carbon disulfide and hydrogen sulfide and waste water containing zinc during the production process, which seriously pollutes the environment and has a long process flow. The high energy consumption has limited its development as a cord.

Lyocell fiber is a new type of regenerated cellulose fiber. It directly dissolves cellulose pulp in non-toxic N-methylmorpholine-N-oxide (NMMO) aqueous solution to form a cellulose solution, and then passes dry- produced by wet spinning. Compared with the traditional regenerated cellulose fiber, viscose fiber, Lyocell fiber has higher strength and modulus, lower elongation, good dimensional stability, good heat resistance, and the production process is environmentally friendly. In addition, the Lyocell fiber process can directly use cellulose pulp with a high degree of polymerization (such as DP>1000) for spinning, which cannot be achieved by the viscose process. Existing research results have shown that the mechanical properties of Lyocell fibers spun from cellulose with a high degree of polymerization can be greatly improved, especially the modulus can be doubled. Therefore, Lyocell fiber is expected to be used as a new type of cellulose fiber for high-performance tire cord.

At present, there are not many patents related to Lyocell fiber used in cords, among which EP1433881-A2, JP2004211277-A, US2004126577-A1, CA2438445-A1, CN1511980-A, KR2004057550-A, US6852413-B2, US2005079 applied by Korean LEE T etc. -A1 discloses a Lyocell multifilament for tire cord and its manufacturing method, which is prepared by dissolving mixed powder of cellulose and polyvinyl alcohol in NMMO solution to prepare spinning solution, and then prepared by dry-wet spinning Lyocell multifilament for cords. Since the NMMO solvent used in Lyocell production is expensive, it needs to be recovered and recycled in production. However, this method also adds polyvinyl alcohol in addition to the cellulose raw material, and a part of the added polyvinyl alcohol will gradually accumulate in the coagulation bath as the spinning progresses, which will cause difficulties in the recovery of the NMMO solvent in the coagulation bath. In addition, EP1493850-A1, JP2005023508-A, and US2005066646-A1 of Korea's KWON I etc. disclose a method for preparing cellulose cords from a cellulose/NMMO solution, which is to dissolve the cellulose in NMMO Form an initial solution of 0.01 to 3%, lower the solidification temperature of the NMMO solution, and then dissolve more cellulose in the initial solution to obtain Lyocell fibers used as cords by dry-wet spinning. This patent uses The two-step dissolution process produces Lyocell fiber, which increases the complexity of the process, and it has not applied for a patent in China.

The present invention proposes to add a certain proportion of cellulose pulp with medium and high molecular weight (polymerization degree 600-850) to the cellulose pulp with high relative molecular weight (polymerization degree 1000-1450) as raw material, and adopts unique swelling - The spinning dope with better spinnability is prepared by the dissolution process, which greatly improves the mechanical properties such as strength and modulus of the spun Lyocell cord. This method uses pure cellulose pulp as raw material without adding other raw materials, which not only makes the preparation process of Lyocell fiber for cord more simple, but also facilitates the recovery of solvent NMMO, thereby greatly reducing production costs.

Contents of the invention

The object of the present invention is to provide a method for the preparation of lyocell fibers for cords.

In order to solve this problem, the following technical solutions are adopted:

1. Cut the cellulose pulp with a high relative molecular mass with a degree of polymerization of 1000 to 1450 and a medium molecular weight with a degree of polymerization of 600 to 850 into small pieces of 0.5 to 4 cm × 0.5 to 4 cm, and then place these small pieces in Dry and balance under reduced pressure for 6-12 hours to make the moisture content 2-4%;

The N-methylmorpholine-N-oxide (NMMO) aqueous solution was concentrated under reduced pressure to a water content of 24-28%.

2. Mix the dried and balanced pulps with degrees of polymerization of 1000 to 1450 and 600 to 850 in the above 1 at a weight ratio of 100:100/11 to 50, and then mix the mixed pulp with the steamed and thickened pulp in the above 1. The NMMO aqueous solution is added into the dissolving device at a weight ratio of 5:110 to 10:105. After 20 to 40 minutes of static swelling and 20 to 60 minutes of strong stirring at 70 to 110 ° C, the temperature is raised to 80 to 125 ° C. Stir and distill under reduced pressure until the water content of the NMMO aqueous solution in the system is 12% to 14%, that is, a brown transparent Lyocell fiber spinning stock solution is formed.

3. The spinning stock solution obtained in the above 2 is ejected from the spinneret, and after passing through an air gap of 5-300mm (that is, the air layer between the spinneret surface and the coagulation bath surface), it enters the liquid with a weight percentage concentration of 0-300mm. Coagulate into fibers in 20% NMMO aqueous solution.

4. The fibers obtained in the above 3 are introduced into multi-stage rinsing rollers, and rinsed with water for 2 to 20 minutes.

5. Wind the rinsed fiber obtained in the above 4 into a bobbin after being dried continuously at 80-160° C. under a tension of 0-1.0 cN/dtex.

The advantage of the present invention is to adopt the cellulose pulp of high relative molecular mass (polymerization degree 1000～1450) as main raw material, the mechanical property of the Lyocell fiber of spinning is greatly improved; Degree 600～850) the method for the cellulose pulp is beneficial to improve the spinnability of high degree of polymerization cellulose spinning solution; Solvent N-methylmorpholine-N-oxide compound (NMMO) used in the present invention has non-toxic And the characteristics of high recovery rate, friendly to the environment; the present invention uses pure cellulose pulp as raw material, does not add other auxiliary raw materials, and adopts unique swelling-dissolving process, so that the preparation of spinning stock solution, the production of Lyocell cord and The NMMO solvent recovery process is simpler and more advanced; the Lyocell fiber prepared by the invention has high strength and modulus, good dimensional stability, and good heat resistance, and can be used as an excellent tire cord, opening up the application field of the Lyocell fiber.

Detailed ways

Example 1

Cut the cellulose pulp with degrees of polymerization of 1418 and 823 into small pieces of 2cm×2cm with a pulp chopper, and dry and balance these small pieces at a vacuum degree of -9×10 ⁴ Pa and 50°C for 10 hours to make them contain water The rate is 2%; 65.4 kg of NMMO aqueous solution with a water content of 50% is distilled under reduced pressure to obtain 44.2 kg of NMMO aqueous solution with a water content of 26%.

Mix 2 kg of dried cellulose pulp with a degree of polymerization of 1418 and 0.4 kg of pulp with a degree of polymerization of 823, and place them in a dissolution tank together with the above-mentioned evaporated NMMO aqueous solution, and pass through 40 minutes at 100 ° C. After static swelling and vigorous stirring for 40 minutes, the temperature was raised to 110° C., stirred and distilled under reduced pressure until the water content of the NMMO aqueous solution in the system was 13%, and a brown transparent spinning stock solution was obtained.

Then the obtained spinning dope is sprayed out from the spinneret, and after passing through an air gap layer with a length of 7 cm, it enters an NMMO aqueous solution with a concentration of 10% by weight and solidifies into fibers. The resulting fibers were introduced into a multi-stage rinse roll and rinsed with water for 15 minutes.

Then, under the tension of 0.2cN/dtex, the washed fiber is continuously dried by a hot roller with a temperature of 100°C and then wound into a bobbin.

The dry strength of the obtained Lyocell fiber was 6.84 cN/dtex, the initial modulus (3%) was 105.3 cN/dtex, and the elongation at break was 7.2%. The fiber has good dimensional stability, its boiling water shrinkage rate is 0.9%, and the fiber has excellent heat resistance, and its dry heat shrinkage at 180°C is less than 1.5%.

Example 2

Cut the cellulose pulp with a degree of polymerization of 1260 and 657 into small pieces of 3cm×3cm with a pulp chopper, and dry and balance these small pieces at a vacuum degree of -9×10 ⁴ Pa and 50°C for 8 hours to make them contain water The rate is 3%; 62.6 kg of NMMO aqueous solution with a water content of 50% is distilled under reduced pressure to obtain 43.5 kg of NMMO aqueous solution with a water content of 28%.

Mix 3.3kg of dried cellulose pulp with a degree of polymerization of 1260 and 0.3kg of pulp with a degree of polymerization of 657, and put them in a dissolution tank together with the above-mentioned evaporated NMMO aqueous solution, and pass 30min at 80°C After static swelling and 30 minutes of vigorous stirring, the temperature was raised to 90°C, stirred and distilled under reduced pressure until the water content of the NMMO aqueous solution in the system was 14%, and a brown transparent spinning solution was obtained.

Then the obtained spinning dope is sprayed out from the spinneret, and after passing through an air gap layer with a length of 5 cm, it enters an NMMO aqueous solution with a concentration of 17% by weight and solidifies into fibers. The resulting fibers were introduced into a multi-stage rinse roll and rinsed with water for 20 minutes.

Then, under the tension of 0.5cN/dtex, the washed fiber is continuously dried by a hot roller with a temperature of 140° C. and then wound into a bobbin.

The dry strength of the obtained Lyocell fiber was 6.24 cN/dtex, the initial modulus (3%) was 86.2 cN/dtex, and the elongation at break was 8.1%. The fiber has good dimensional stability, its boiling water shrinkage rate is 1%, and the fiber heat resistance is also excellent, and the dry heat shrinkage at 180°C is less than 1.5%.

Example 3

Cut the cellulose pulp with a degree of polymerization of 1130 and 728 into small pieces of 2cm×2cm with a pulp cutter, and dry and balance these small pieces at a vacuum degree of -9×10 ⁴ Pa and 50°C for 6 hours to make them contain water The rate was 2%; 64.8kg of NMMO aqueous solution with a water content of 50% was distilled under reduced pressure to obtain 42.6kg of an NMMO aqueous solution with a water content of 24%.

Mix 2.3kg of dried cellulose pulp with a degree of polymerization of 1130 and 0.9kg of pulp with a degree of polymerization of 728, and place them in a dissolution tank together with the above-mentioned evaporated NMMO aqueous solution, and pass 20min at 93°C After static swelling and 50 minutes of vigorous stirring, the temperature was raised to 100°C, stirred and distilled under reduced pressure until the water content of the NMMO aqueous solution in the system was 12%, and a brown transparent spinning solution was obtained.

Then the obtained spinning stock solution is sprayed out from the spinneret, and after passing through the air gap layer with a length of 5 cm, enters the pure aqueous solution to solidify into fibers. The resulting fibers were introduced into a multi-stage rinse roll and rinsed with water for 8 minutes.

Then, under the tension of 0.8cN/dtex, the washed fiber is continuously dried by a hot roller with a temperature of 120° C. and then wound into a bobbin.

The dry strength of the obtained Lyocell fiber was 6.05 cN/dtex, the initial modulus (3%) was 71.6 cN/dtex, and the elongation at break was 8.5%. The fiber has good dimensional stability, its boiling water shrinkage rate is 1%, and the fiber heat resistance is also excellent, and the dry heat shrinkage at 180°C is less than 1.5%.

Claims (6)

1. for the preparation method of the lyocell fiber of cord, it is characterized in that: A) the cellulose pulp with the moisture content of 2～4% and the degree of polymerization of 1000～1450 and 600～850 are mixed with the weight ratio of 100:100/11～50 with the moisture content of dried equilibrium 2～4% respectively; Above-mentioned mixture and moisture content are 24-28% N-methylmorpholine-N-oxide aqueous solution is added to the dissolution device at a weight ratio of 5:110-10:105, and after static swelling and strong stirring at 70-110°C, the temperature is then raised to 80-125°C, after stirring and vacuum distillation until the water content of N-methylmorpholine-N-oxide aqueous solution in the system is 12%-14%, a brown transparent lyocell fiber spinning solution is formed; B) The lyocell fiber spinning dope obtained in the above A) is ejected from the spinneret, and after passing through an air gap, it enters an aqueous solution of N-methylmorpholine-N-oxide with a concentration of 0 to 20% by weight solidified into lyocell fibers; C) introducing the fiber obtained in the above B) into a multi-stage rinsing roller, and rinsing with water for 2 to 20 minutes; D) Continuously drying the rinsed lyocell fibers obtained in the above C) and winding them into bobbins. 2. The method for preparing lyocell fibers for cords as claimed in claim 1, characterized in that the cellulose pulp with a degree of polymerization of 1000 to 1450 or 600 to 850 in A) is cut into Small pieces of 0.5-4cm x 0.5-4cm are obtained after drying and equilibrating under reduced pressure for 6-12 hours. 3. the preparation method of the lyocell fiber that is used for cord as claimed in claim 1 is characterized in that the N-methylmorpholine-N-oxide aqueous solution described in above-mentioned A) is in advance under reduced pressure condition Evaporate and concentrate until the water content is 24-28%. 4. the preparation method of the lyocell fiber that is used for cord as claimed in claim 1 is characterized in that the static swelling described in above-mentioned A) and strong stirring is that pulp mixture and water content are 24～28% The N-methylmorpholine-N-oxide aqueous solution is statically swelled in a dissolving device for 20-40 minutes, and then vigorously stirred for 20-60 minutes. 5. the preparation method of the lyocell fiber that is used for cord as claimed in claim 1 is characterized in that the air gap between the surface of the spinneret described in above-mentioned B) and the coagulation bath surface is 5～300mm . 6. The preparation method of lyocell fiber for cord as claimed in claim 1, characterized in that the continuous drying described in the above D) is under the tension of 0.2～1.0cN/dtex, 80～160 ℃ continuous drying.